Here's the one I'd love to model: the funicular of the Eureka Mill, which transferred ore from the V&T down to the tiny Eureka RR below.

This is from a copyrighted page, so here's the full credit: "Thirty Inch Gauge Railroads: the Eureka Railroad," article by Mallory Hope Ferrell, photos from author's collection; Narrow Gauge & Short Line Gazette, Nov-Dec 2005, p66.

The following users say thanks to Cliff Jennings for this useful post:

That smelter complex looks incredibly cool. Would make an awesome model even in HO, assuming you could get enough prototype info to make it. Of course in G, you'd need about an acre of land just for that!